CVE-2026-55247
Authenticated editor can trigger SSRF, DoS, and stored XSS via iCalendar import.
Is CVE-2026-55247 being exploited?
Not confirmed. CVE-2026-55247 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.34% probability of exploitation in the next 30 days.
How severe is CVE-2026-55247?
CVE-2026-55247 is rated Critical with a CVSS score of 9.1. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-55247?
Yes. A fix has been recorded for CVE-2026-55247. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-55247 affect?
CVE-2026-55247 affects plone.app.event versions prior to 5.2.4 and 6.0.1, Plone CMS sites using plone.app.event. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-55247?
Upgrade plone.app.event to 5.2.4 or 6.0.1; restrict editor access; block outbound HTTP from app.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Authenticated editor can perform SSRF to internal hosts/files, exhaust resources (DoS) by importing large/many events, and store malicious event URLs that cause XSS in other users' browsers.
Immediate action required
- affected< 5.2.4
- affected>= 6.0.0 and < 6.0.1
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.